The applicant's long term research objectives are to use advanced technology to help improve the quality of life of wheelchair users, especially those with disabilities from spinal cord injury (SCI). More specifically, the applicant sets his target at preventing the soft tissue breakdown, the most common secondary complication of wheelchair sitting, by reducing or eliminating risk factors. In the US, nearly 50% of the 1.4 million people who rely on wheelchairs for mobility develop serious tissue breakdown at pressure point areas such as the ischia and the greater trochanters. This has a detrimental impact on the quality of life of the affected population and imposes a tremendous economic burden to health care. In this study, the applicant focuses on development and optimization of the sophisticated computational finite-element (FE) modeling theory and technology to investigate the soft tissue response to external sitting loads. The proposed FE models will simulate the load-bearing condition as in real sitting. It is expected that the models will not only be powerful tools for better understanding the response of soft tissues to sitting loads, but they will also facilitate development of improved prevention and treatment strategies against the soft tissue breakdown. Aim 1: To develop and refine the methodology for establishing the geometry of FE models for the buttock-thigh. The methodology implements a true representation of the anatomical geometry of buttock-thigh structure in actual sitting. Four versions of these models will be established representing males and females, each including able-bodied and chronic spinal cord injury (SCI) individuals. The models will also be calibrated and validated. Aim 2: To implement into the FE model the experimentally acquired mechanical properties of biological soft tissue (both human and experimental animal) under healthy, wounded, and SCI conditions;to investigate the sensitivity of the FE modeling to the variation of the material properties and the contact behavior among tissue layers;and to investigate the variation of buttock tissue properties in intact and SCI populations. Aim 3: To evaluate the buttock tissue internal mechanical environment in the sitting posture in individuals with chronic SCI using the validated FE models, and compare the FE model predictions with those obtained from the able-bodied controls. Relevance to Public Health: This research will provide a better understanding of the etiology of soft tissue breakdown in wheelchair sitting and help finding better strategies of treatment and prevention.